TWI512317B - Coated light emitting device and method for coating thereof - Google Patents

Description

Coating light emitting device and coating method thereof

The invention relates to a light-emitting device comprising a light-emitting diode disposed on a sub-substrate, the device having a lateral circumferential surface and a top surface, and a photo-active coating layer. A method for applying the coating layer to a light-emitting device is also disclosed.

Today, high power lighting devices containing light emitting diodes (LEDs) are used in an increasing number of lighting applications. In general, two material systems for making high power LEDs are used.

InGaN is used to produce high efficiency blue LEDs.

AlInGaP is used to produce highly efficient red and amber LEDs.

Both material systems suffer from severe efficiency losses when their material compositions are altered to shift wavelengths from blue to green and from red to green.

By coating a wavelength converting material, such as a fluorescent and/or luminescent material, in the light path, the emission wavelength can be adapted to a number of specific wavelengths. Blue and/or UV-emitting LEDs are particularly suitable for use as light sources in such light-emitting diodes (or wavelength-converting light-emitting diodes) due to the fact that wavelength-converting materials typically absorb light emitted by the diodes. Light having a higher wavelength (red displacement) is emitted at least in part.

The InGaN system can be combined with the wavelength converting material or optical component (eg, a phosphor material) to convert portions of high energy, low wavelength blue light to lower energy, higher wavelengths. In this way, a white LED (typically using a YAG:Ce phosphor) can be produced by combining a blue LED with a suitable phosphor on the LED, or the blue LED can be converted to green, yellow using a suitable phosphor material. , amber or red LED. This color conversion is accompanied by loss of efficiency (mainly Stokes displacement loss), but the high initial efficiency of the blue LED makes the uniform conversion to amber and red completely attractive for guiding the AlInGaP system that is subject to thermal efficiency problems. replacement.

JP 2002353507 discloses an illuminant in which a luminescent substance that changes the emitted light to another color is stabilized. This is achieved by filling a plurality of grooves inside the LED with a resin-containing phosphor as a grain binder for stabilizing the total amount of the resin.

Conventional LED phosphor technology uses phosphor pigments or powder particles embedded in a resin on top of the LED. However, this results in backscatter loss and processing variations. A new technique uses a ceramic phosphor technology called "Lumiramic" technology (Lumiramic converter is described in US 2005/0269582 A1). This technique makes it possible to produce high gloss and thermally stable ceramic phosphor platelets with well defined thicknesses and geometries to match the LED geometry (which is typically square, 1 x 1 mm). By controlling the porosity in such phosphor bodies or phosphors, the angular path length difference can be sufficiently disturbed/scattered to provide a fairly uniform cross-angle color performance while sacrificing toward the LED via backscattering Some light.

By using the Lumiramic technique, a white LED can be made by partial conversion of blue light to a higher wavelength (using, for example, a YAG:Ce phosphor). Again, green, amber, and red LEDs can be made by attempting to fully absorb the blue LED light and efficiently convert it to a chromatogram that matches the green, amber, or red characteristics.

However, this small plate phosphor technology requires that the non-negligible thickness of the phosphor be comparable to the size of the LED. The phosphor typically has a thickness of about 120 [mu]m in the size of 1 x 1 mm for white LEDs. This causes a significant contribution to the light emission from the four lateral or lateral surfaces of this squared volume.

Furthermore, the LED itself has a lateral surface with non-negligible light extraction. The LED wafer can be of the "flip-chip" type in which two leads are positioned on the same side of the wafer. This design facilitates the configuration of the wavelength converting body on the light emitting surface of the device. In "flip-chip" LED technology, an LED is mounted on a substrate or a light transmissive body. This sapphire substrate, which typically has a thickness of 100 μm, also provides significant lateral surface contribution when the substrate (usually sapphire) is not removed. To solve this problem, the substrate can be removed during a lift off process. Also, an InGaN LED stack consisting of a quantum well and an anode, a cathode, and a reflector can have a thickness of about 10 [mu]m and be composed of a material having a high refractive index, resulting in a relatively large waveguide and non-negligible side emission.

The bonding layer connecting the LED to the Lumiramic phosphor increases the lateral surface thickness and typically has a thickness of 10 μm.

Examples of the bonding material include, for example, a polyoxymethylene resin.

Disadvantages associated with light emitted by the lateral (edge) surface of the self-illuminating device are as follows: unconverted light (such as blue light) leaking from the edge of the edge of the LED and the edge of the binder. For partially converted Lumiramic, this can result in significant blue light and significant changes in blue light flux present at large angles relative to the normal direction, and thus reduce cross-angle color uniformity and consistency. Changes in layer thickness, such as thickness of the layer (such as thickness of the binder) and phosphor placement, which occur during processing, result in a change in blue light leakage from the side. For fully converted Lumiramic, blue light leakage greatly reduces the color purity of green, amber or red LEDs. In addition, this light leakage reduces efficiency because portions of the blue light are not converted to the desired color.

The wavelength conversion through the lateral edges of the phosphor differs from the converted spectrum of the top surface of the phosphor due to the difference in path length between the light emitted from the side and the light emitted from the top surface. This is especially desirable for fully converted phosphors because the color purity of the LEDs is reduced by incomplete conversion of the sides of the phosphor.

Partially (approximately half) of the lateral surface is directed downwards, returning to the luminous flux emission of the sub-substrate positioned generally close to the LED dies. In general, the light emitted to the wrong side and the light emitted to the top direction but at a large angle to the normal direction are difficult to be effective in an optical system (such as a collimator optics, lens, etc.) combined with the light source. Captured, and therefore potentially reduces system efficiency. Similarly, the downward flux interacts with the submount and will typically be partially absorbed, partially reflected and typically affected by color interaction with the surface of the submount. Light scattered or reflected from the sub-substrate also increases the LED source area and causes stray light, which is undesirable for light spread critical applications such as automotive forward illumination or projection LED systems.

An increased amount of light that is comparable to the surface area of the active LED. This is caused by the increased surface area of the phosphor surface corresponding to the surface area of the LED. Even if the phosphor top surface area is similar to an LED, the phosphor side will still contribute to an increased source area. This is especially important in light spread critical applications such as automotive forward lighting, camera or video flash modules or projection LED systems.

In summary, various embodiments of the illumination device suffer from the disadvantages associated with Lumiramic and/or the edge layers of the bonding layer and/or LED dies. These shortcomings are primarily related to color variations or limited color purity due to spectral differences between the side emission and the top emission that are not pleasing to the eye. Furthermore, there will be a wavelength-converted light flux emission that is directed (approximately half) from the lateral surface to the side and sideways, which is difficult to effectively use in coating. In addition, the amount of light spread can be increased compared to the surface area of the active LED, which is one of the disadvantages of light spread critical applications such as projection LED systems, automotive headlights or spotlights.

A method for coating a light-emitting device has been disclosed in US 2005/0062140, which uses a mold for coating a material having light-converting particles on an LED device. However, this method involves a particular coating apparatus and is laborious and expensive.

Accordingly, there is a need for a light emitting device and a method for producing the same that does not suffer from color variations or purity that are not desired due to light emission through the lateral edges of the light emitting device. Loss of efficiency, or provide an increased amount of light that is comparable to the surface area of the active LED.

It is an object of the present invention to at least partially overcome such problems, and to provide a light emitting device and a method for producing the same that does not suffer from the efficiency of scattering due to light passing through the lateral surface of the light emitting device loss.

Therefore, according to a first aspect, the present invention provides a light-emitting device 1 comprising a light-emitting diode 2 disposed on a sub-substrate 3. The device has a lateral circumferential surface 6 and a top surface 8, and a photoactive coating layer 7. The coating layer 7:

- covering at least a portion of the circumferential surface 6,

- extending from the sub-substrate 3 to the top surface 8, and

- Essentially not covering the top surface 8.

When at least a portion of the lateral circumferential surface of the illumination device is covered from the sub-substrate to the top surface by a photoactive coating layer but does not substantially include the top surface, control of light escape from the lateral surface. In this way, light can be increased, for example, at the top surface.

In an embodiment of the invention, the photoactive coating layer is selected from the group consisting of a reflective coating layer, a diffusion coating layer, a spectral filter coating layer, a luminescent coating layer, and a light blocking coating layer, and combinations thereof group.

When the photoactive coating layer is used to coat the lateral circumferential surface, the coating layer will become reflective, diffuse, spectrally filtered, luminescent, or opaque, depending on the selection.

In an embodiment of the invention, the device further includes an optical component 4 disposed on the LED, the optical component 4 being selected from the group consisting of a phosphor, a light transmissive body, and a reflector, and combinations thereof. group.

In an embodiment of the invention, the reflector is configured such that light will escape through at least a portion of the lateral circumferential surface.

In an embodiment of the invention, an optical component disposed on the light emitting device is further included.

In an embodiment of the invention, the coating layer is a solid. The lateral circumferential surface can also be coated by more than one coating layer.

In an embodiment of the invention, the illumination device according to the invention may be arranged in an array.

By arranging the light-emitting devices according to the present invention having a coating layer on the lateral circumferential surface in an array, optical crosstalk can be avoided, for example, between individual light-emitting devices. Therefore, the illuminating devices can be individually addressed.

The array of light emitting devices can also be configured to share a coating layer.

According to a second aspect, the invention provides a method for applying a coating layer on at least a portion of a lateral circumferential surface 6 of a light-emitting device 1 comprising a light-emitting diode. The method comprises disposing a photoactive coating layer 7 on at least a portion of the circumferential surface 6, the coating layer 7 extending from the submount 3 to the top surface 8, and not covering the top surface 8 in nature.

The inventors have recognized that a fast and simple coating process can be achieved by using the method of the present invention to coat the lateral circumferential or lateral edges of the illumination device. Coating of the device can additionally be achieved by using capillary forces to coat the lateral circumferential surface. Due to the tuned optical properties of the solid coating layer and the coating formed on the lateral circumferential surface, the light properties of the lateral edges of the escaping illumination device are controlled.

In an embodiment of the invention, the method further comprises the steps of:

Applying a first liquid coating composition on the sub-substrate 3,

Allowing the first coating composition to cover at least part of the first lateral circumferential surface 6 of one of the illumination devices 1 and

- solidifying the first coating composition to obtain a first solid coating layer 7 on the at least a portion of the first lateral circumferential surface 6.

In an embodiment of the invention, the coating composition is allowed to cover at least a portion of a first lateral circumferential surface 6 by capillary force.

In an embodiment of the invention, the coating composition is applied by a method selected from the group consisting of needle dispensing, nozzle dispensing, printing, and by spraying.

When such coating methods are used, the exact amount of coating composition can be achieved. Therefore, it is possible to control the amount of the coating layer by controlling the amount of the coating composition used.

In an embodiment of the present invention, the liquid coating composition forms a coating selected from the group consisting of a reflective coating layer, a diffusion coating layer, a spectral filter coating layer, a light-emitting coating layer, and a light-blocking coating layer after solidification. And a solid coating layer of the group of combinations thereof.

When the solid coating layer is formed, light leakage from the lateral circumferential surface of the light-emitting device can be controlled. Thus, for different purposes, the coating composition can be selected to form a reflective, diffuse, spectrally filtered, luminescent or light-blocking layer.

The coating composition may comprise a sol-gel derived material or a polyoxynoxy resin.

In an embodiment of the invention, when a polar coating composition is used, the lateral circumferential surface can be pretreated to become polar. Alternatively, the lateral circumferential surface can be treated to become non-polar and a non-polar or polar coating composition can be used.

When the submount and the lateral circumferential surface are pretreated in this manner, the polar coating composition will be promoted by capillary forces to cover the submount. By treating only a portion of the sub-substrate and the lateral circumferential surface to become polar, it is possible to coat only portions of the lateral circumferential surface. Therefore, it is also possible to obtain a portion of the lateral circumferential surface free of the coating layer. Similarly, a non-polar coating composition can be applied to a surface that has been pretreated to become polar or non-polar to coat selected portions of the lateral circumferential surface.

In an embodiment of the invention, the method further comprises the steps of:

Applying at least one second liquid coating composition on the sub-substrate,

Allowing the second coating composition to cover at least a portion of the second lateral circumferential surface of one of the illumination devices, and solidifying the second coating composition to obtain a second portion on the at least a portion of the second lateral circumferential surface Solid coating layer.

The first coating composition can be different from the second coating composition in one embodiment.

Due to the use of different materials in the first coating layer and the second coating layer, it is possible to achieve different solid coating layers with reflective, diffuse, spectral filtering, luminescent, and optical blocking optical functionality. Thus, the same lateral circumferential surface can be coated by more than one coating layer having the same or different optical functionality.

The first lateral circumferential surface may be different from the second lateral circumferential surface in another embodiment.

When different lateral circumferential surfaces are coated by different solid coating layers, portions of the lateral circumferential surface receive different optical functionality.

It should be further noted that the present invention pertains to all possible combinations of technical solutions.

These and other embodiments are described more in the embodiments.

This and other aspects of the present invention will now be described in more detail with reference to the accompanying drawings in which, As an example, the figures show a reflective coating layer. However, the coating layer can also be luminescent, colored, scattering, and absorbing. The figures are not necessarily drawn to scale.

Hereinafter, an embodiment of a light-emitting device according to the present invention will be described in more detail.

Accordingly, an embodiment of the apparatus of the present invention is illustrated in FIG.

Therefore, in this embodiment, a light-emitting device 1 including a flip-chip LED 2 is disposed on a sub-substrate 3. On the LED 2, an optical component 4 (in this embodiment, phosphor 4a, ie Lumiramic) is configured to receive the light emitted by the LED 2. The bonding layer 5 is used to connect the phosphor 4a and the LED 2. A coating layer 7 having reflective functionality is disposed on the lateral surface or lateral circumferential surface 6 of the illumination device 1 such that light does not substantially escape through the lateral surface 6 of the illumination device 1. Instead, the light is reflected to eventually exit via the top surface 8 of the phosphor 4a.

As used herein, lateral, lateral, lateral, and lateral circumferential surfaces refer to the lateral surface area around the light emitting diode, but do not include the top surface area.

In the set of rays I, the blue light generated at the p, n junction is transmitted to the bonding layer and incident on the side coating, resulting in diffuse backscattering of the bonding agent, phosphor or LED.

In ray collection II, blue light is not converted in the phosphor and reflected back to the phosphor. A portion of the reflected light is extracted via the top surface.

In the light collection III, the generated light is guided in a high-index InGaN material (n = 2.7) and incident at the edge where the light is back-reflected by the side coating. The angular redistribution during backscattering helps to overcome the entrapment of light by the waveguide. This portion of the light is thus extracted from the LED to the binder and phosphor layer.

In the light collection VI, blue light is absorbed in the phosphor and converted to, for example, red light. The red light travels in the direction of impacting the lateral surface and is backscattered and partially extracted via the top surface. Since the collection of rays is similar in embodiments similar to each other, not all embodiments contain a specific reference to the collection of rays.

Many variations of Example 1 are perceptible. For example, a fully converted or partially converted phosphor top emitter can be used. For complete conversion, the phosphor absorbs blue light and converts it to another color with a higher wavelength. This amount depends on the Lumiramic thickness and concentration and absorption coefficient of the luminescent center in the phosphor. Try to achieve a sufficiently large path length in the phosphor to convert almost all blue light to a larger wavelength, such as green, amber or red. Due to the side coating, the cross-angle color performance is very good, that is, there is no blue light leakage at a large angle.

Another embodiment of the apparatus of the present invention is illustrated in FIG.

This embodiment is similar to Embodiment 1 except that the side of the phosphor 4a is angular and has a depending on the LED. The reflective coating is present on the right and left side faces but at different angles.

In this case, the phosphor size is larger than the LED size. The bonding layer between the LED and the phosphor can substantially cover the LED area or a larger phosphor area. If the bond area is smaller than the phosphor area, only the overhang area may be filled with a coating to, for example, obstruct the side emission of the LED and/or the adhesive so as not to cover the lateral sides of the phosphor. Alternatively, both the overhang area and the sides of the phosphor can be covered. Furthermore, the overhangs can have different shapes, such as angles or squares.

The phosphor may also be insufficiently large relative to the area of the LED, or the placement of the phosphor may be inaccurate such that the LED area is not adequately covered, but both the overhang or tilt are displayed in a particular direction. The side coating provides a means to cover and block the direct emitting portion of the LED. Lumiramic, which is not big enough, has better bonding and placement accuracy in production.

The bond area can be extended beyond the LED area and the phosphor area, and portions of the bond material can cover portions of the LED and the lateral sides of the phosphor.

The coating may extend only over a portion of the lateral surface or the entire surface as long as it extends from the sub-substrate to the top surface, but does not include the top surface. It is possible to coat only Lumiramic or to coat LEDs. This is achieved by tuning the sub-substrate of the illuminating device and the wetting behavior of the lateral surface.

In another embodiment, it is also possible to apply under the LED (here, making electrical contact with the submount). Due to electrode patterning, some of the light will leak through the gap between the electrodes or mirrors. This light can be guided at the tail of the LED where it will likely be absorbed. If a reflective side coating is used, this light is backscattered to the LED for reuse.

When a reflective coating layer is used, it can also be spread on the sub-substrate surround to increase the reflectivity of the sub-substrate and thereby reduce the light loss of any light that is directed back to the LED.

In another embodiment, a dome can be added to the illumination device.

Yet another embodiment of the apparatus of the present invention is illustrated in FIG.

This embodiment is similar to Embodiment 1, but has two coating layers 7a and 7b. The first coating layer 7b is transparent, and the second coating layer 7a is reflective. Other combinations of functionality and number of layers are also possible. However, a benefit in the case of this combination of coatings may be the opportunity to fill a portion of the bonding layer or to fill an incompletely existing area. For example, a change in the bonding process can result in a layer that does not completely adhere to the gap between the die and the LED. This may first be filled with a transparent layer and then covered with, for example, a reflective layer. Otherwise, the reflective layer will fill the gap and cause a portion of the luminous flux that will block the light loss. Other combinations of coating layers may of course be possible.

Another embodiment of the apparatus of the present invention is illustrated in FIG.

Therefore, in this embodiment, a light-emitting device 1 including a flip-chip LED 2 is disposed on a sub-substrate 3. On the LED 2, the substrate 4b still exists. A coating layer 7 having reflective functionality is disposed on the lateral surface 6 of the illumination device 1 such that light does not substantially escape through the lateral surface 6 of the illumination device. Instead, the light is reflected to eventually exit through the top surface 8 of the substrate 4b. In Figure 4, three ray paths are shown. The ray path I indicates that light is guided in the LED to the edge that is reflected back from the coating. Light path II shows the light path through the sapphire substrate with side reflections. Ray Path III shows the direct emission ray path without interaction with the sides.

Therefore, a combination of different reflective coating layers, absorption coating layers, colored coating layers, diffusing coating layers, and luminescent coating layers and coating layers may be present on the lateral surfaces. It is also possible to coat only a portion of the surface. Combinations of LEDs with substrates such as sapphire and phosphors are also possible.

In a diffuse coating layer, incident light is transmitted primarily with minor deviations from its light path (a small amount of incident light can be subjected to multiple scattering events and still be reflected). This diffusivity helps to disturb angle-dependent color effects, that is, to mix light at different locations and angles. Preferably, the side coating has a limited optical thickness, such as from 10 μm to 100 μm, but this is not strictly necessary. In this case, the area of the source is not significantly amplified by the scattering event, and the center of the scattering can be considered as a new source of light.

In another embodiment, the side coating is painted to absorb blue light and transmit yellow or amber or red light. Due to the side coating, blue light leakage at large angles is suppressed while still transmitting converted light. Blue light absorption will result in lower efficiency compared to reflective side coatings. However, the converted light will be used more efficiently because it can be easily extracted from the pcLED and also extracted from the side.

In another embodiment, an absorbent side coating for wavelengths worth considering is contemplated, which generally means that the coating is absorbent for visible light, that is, the coating is black. This condition is less favorable for obvious efficiency reasons. However, light leakage from the side is highly inhibited, but this applies to both blue and converted light (unless the converted light is in the infrared, assuming the black coating is transparent in IR).

In another embodiment, the illumination device has a luminescent side coating wherein the blue light is (partially) absorbed and converted to a higher wavelength and re-emitted. The side coatings may contain phosphor particles similar to Lumiramic phosphor materials (eg, partially converted white YAG:Ce). The side coating may also contain phosphor particles that are different from the Lumiramic material. For example, the red phosphor contains a side coating to make the white light emission from the Lumiramic phosphor warmer in color, that is, a warm white configuration.

Another embodiment of the apparatus of the present invention is illustrated in FIG.

Therefore, in this embodiment, a side-emitting light-emitting device 1 including a flip-chip LED 2 is disposed on a sub-substrate 3. A Lumiramic phosphor 4a is disposed on the LED 2. A reflected light reflector 4c is disposed on the phosphor. The coating of the lateral surface 6 prevents transmission of light from one or more sides and reflects and recycles the light to transmit it to the uncoated side. For a square Lumiramic, only one lateral surface, or two surfaces or three surfaces or portions of each of the surfaces may be coated. For example, one of the Lumiramic corners can also be left open to emit light from the corner area. The side reflective coating and the top reflective coating can form a single layer, such as a highly scattering reflective coating layer.

In one embodiment of a 1 x 1 mm configuration, the lumen efficiency is the first lateral surface coated with a phosphor thickness of 250 μm and a 100% lumen efficiency of the uncoated side emitter. 95% of the cloth LED, the second lateral surface is coated with 78% of the LED, and the third lateral surface is coated with 56% of the LED. The portion of the light is therefore lost in the LED, but forces the remaining flux to pass through the smaller area and to the particular side. The brightness of the lateral surface is thus increased. This is important in, for example, backlighting applications or light guide lighting fixture designs where light should be effectively coupled into a thin light guide to position the light source at the sides of the light guide panel.

Yet another embodiment of the apparatus of the present invention is illustrated in FIG.

In this embodiment of the side-emitting light-emitting device (similar to Example 5), a substrate is still present on the LED below the phosphor. The coating layer is only present on the LED and the substrate and is not present on the phosphor.

As an alternative, the reflector can be disposed directly on the substrate. The coating can be present on the lateral surface of the substrate without the use of a reflective side coating that does not leak a significant amount of blue light from the side of the LED substrate. The phosphor can also extend beyond the area of the LED substrate (its size is too large).

However, the side-emitting light-emitting device may also have other types of coating layers, such as a diffuse coating layer or a light-emitting coating layer. By using a diffuse side coating, the angle of the side emission and the spectral distribution can be affected, for example, to make it more uniform.

By using a side coating that absorbs blue light and transmits converted light (eg, amber light), a fully converted side emitter can be made with high color purity.

Different optical functionality can be achieved at different lateral surfaces by dispensing at both sides, for example, a reflective coating can be added to the first, second or third lateral surface, and on the other side A blue absorbing coating is added and a converted light-emitting colored coating is applied.

Thus, in another embodiment, a reflective side coating is deposited on at least one side of the LED and a colored side coating is deposited on the other side. This can be used to produce a high color purity side emission fully converted LED having one, two or three emitting lateral surfaces.

Phosphor coated LEDs (pcLEDs) are particularly useful, for example, in high brightness or light spread limited applications such as spotlights, flash LED modules, projection displays, and automotive headlamps.

For some of these applications (for example, in an adjustable spotlight or in a vehicle headlight that illuminates into a curved shape), the LEDs need to be individually addressable, so each individual LED can be turned on as desired by the user/condition / cut or dim.

One of the problems in the case of LED arrays that can be individually addressed in an array is that the pump light of one LED can easily reach the phosphor of one of the adjacent LEDs in the array. This can, for example, cause the lamp to provide an erroneous output spectrum or the LED is turned "on" in the headlights, which should be in the off state.

Yet another embodiment of the apparatus of the present invention is illustrated in FIG.

In this embodiment, an array of illumination devices having varying colors is applied. The Lumiramic phosphor is used to obtain R = red light, G = green light, and W = white light, and the sapphire substrate B is used to obtain blue light from the light-emitting device. The reflective coating is disposed on the lateral surface around and between the light emitting devices such that the light emitting device even shares the coating layer.

The array can be 1 or 2 dimensional. The gap between the LEDs can be filled with a reflective coating by capillary force or by plotting. The gap between the LEDs can also be partially filled or filled with a layer of different functionality, such as a transparent, luminescent, diffusing, colored or luminescent layer. The LEDs can be driven simultaneously (such as when placed in series), or the LEDs can be driven independently. The arrays can also be of the same color and the coating can be disposed only on the lateral surface of the device such that the coating is not shared between the devices. The array may also be composed of LEDs each having its individual side coatings, in which case the coating layer is not shared.

In particular, a LED array with a red fully converted Lumiramic, a green fully converted Lumiramic, a blue LED with a substrate, and optionally a white Lumiramic is included. In general, the thickness of various phosphors and/or substrates can vary. The side coating can accommodate these height differences. The reflective coating will inhibit optical crosstalk between the LEDs to produce an array of LEDs having a wide range of high purity colors when the LEDs are individually addressable. This produces a light source with a color mixing maximum window (i.e., any mixture of such colors from a very pure color to a spanned color range in the color map). This is important for, for example, a color controlled LED source or a full illumination source for a spotlight.

When optical mixing is required over a small distance, the side coating between the LEDs can be made transparent or diffuse, however, in some cases, optical crosstalk between the LEDs will affect performance. For example, when only the red LED is turned on, the blue light generated from this LED will also be able to excite adjacent green phosphors to also produce some green.

To prevent this crosstalk while still maximizing the mixing capability, a colored or luminescent colored coating can be applied between the LEDs that absorbs the blue light that travels from one LED to the next. In the case of a luminescent coating, this blue light will again be converted to another color.

In another embodiment, a square array, such as a 2 x 2 array, can be used. Alternatively, instead of a 1×4 array, a larger array can be similarly made, such as 4× with alternating RGBW, GBWR, BWRG, WRGB (R=red, G=green, B=blue, and W=white) colors. 4 arrays.

In yet another embodiment, the LED can be subdivided by a high color purity region by coating the phosphor array on a single LED and using a side coating, where the x, y colors correspond to the red, green, and blue colors in the color map. Location-dependent coordinates. Light emission from such colored areas will be mixed depending on the distance to the LED. Advantageously, the colors can be made from pure RGB colors to obtain white LEDs that can be combined and matched to an array of RGB color filters in applications such as LCD backlights or projection displays. (YAG: Ce partial conversion Lumiramic is a white LED that is not self-mixing solid color, and therefore is not suitable for combination with color filters). The area between the phosphors can be made transparent or diffuse to promote light mixing. The outer coating is preferably reflective to minimize color masking at the sides of the LED.

In another embodiment, an array of side-emitting Lumiramic LEDs is coated. Instead of placing individual fully converted side emitters with side coatings in close proximity to each other, adjacent LEDs can be placed to share a side coating. In this case, the side coating can be considered as an interfacial coating between adjacent LEDs, and the LEDs can be placed closer together. By using a reflective side coating, crosstalk between the LEDs is suppressed to achieve an array of LEDs that can be varied from high purity individual colors to any mixed emission of such colors.

If individual colors are not required and optimal color mixing is required, the coating between the LEDs can be made transparent, diffuse, colored or illuminated. In the first two options, both blue light and converted light can be guided to adjacent LEDs. In the latter two options, blue light will be (at least partially) absorbed, and the converted light will be able to conduct waves to and mix with adjacent pixels.

In another embodiment, the reflective side coating is placed on a Lumiramic phosphor having a line-grid polarizing structure on the surface of the phosphor. In this case, the side of the phosphor that blocks the unpolarized structure leaks unpolarized light.

In summary, the invention is applicable to LED configurations that typically use phosphor conversion. However, the side coating technique can also be applied to normally colored (non-phosphor converted) LEDs. LEDs are suitable for flashlights, automotive headlights or taillights, backlights or full lighting (such as spotlights).

The invention can also be applied to arrays of such LEDs, for example, in LED arrays for automotive forward illumination or in RGB LED arrays for projection illumination purposes or in full illumination color tunable (concentrated) lamps.

As used in this application, the term "light emitting diode" as used herein in the abbreviation "LED" refers to any type of light emitting diode or laser emitting diode known to those skilled in the art (laser emitting diode). It includes, but is not limited to, inorganic-based LEDs, organic small molecule-based LEDs (smOLEDs), and polymer-based LEDs (polyLEDs).

The LEDs used in the present invention can emit light of any color to the IR range from the UV range, via the visible range. However, since the wavelength converting material conventionally converts light by red displacement, it is often desirable to use an LED that emits light in the UV/blue range because the light can be essentially converted to any other color.

The LED chip preferably has a "flip-chip" type in which two leads are positioned on the same side of the wafer. This design facilitates the configuration of the wavelength converting body on the light emitting surface of the device. However, other types of LED chips are also contemplated for use in the present invention.

The wavelength converting material used in the present invention is preferably a fluorescent and/or phosphorescent material which is excited by unconverted light and which emits light upon relaxation. The optical component is typically a phosphor material, such as a ceramic phosphor such as a Lumiramic phosphor.

The fully converted LED is the LED in the case where all of the electrically generated light is converted to the desired color, and the partially converted LED refers to the LED in the case where only the portion of the electrically generated light is converted to another color.

Another aspect of the invention pertains to a method for producing a light-emitting device in accordance with the present invention.

Hereinafter, a method for applying a coating on a lateral surface of a light-emitting device will be described in more detail.

The light-emitting device 1 includes a light-emitting diode (LED) 2 disposed on a sub-substrate 3. A liquid coating composition is added to the sub-substrate 3. The coating composition can be applied in a predetermined amount such that capillary forces can deliver the liquid coating composition to cover the lateral surface of the light emitting device. This amount is usually a small drop or a few droplets. However, depending on the thickness of the desired coating, this amount can also be greater. The liquid volume per 1 x 1 mm area of the LED device can be between 0.01 and 100 microliters, preferably between 0.1 and 10 microliters, and more preferably between 0.5 and 5 microliters. The volume of solids is typically small due to shrinkage during curing of the coating and/or removal of solvent.

In Figures 8a to 8c, a schematic representation of a coating of the lateral surface of the illumination device is shown. Thus, Figure 8a illustrates one drop of liquid placed close to the LED wafer. In Figure 8b, the droplet begins to coat the lateral surface of the device by capillary force. Figure 8c illustrates that the coating of the entire lateral surface has been achieved.

The coating composition is disposed on the submount, adjacent to, or in contact with, the lateral surface of the illuminating device such that the coating composition will cover the lateral surface by capillary forces. The coating composition can be placed, for example, from 0 mm to 2 mm from the lateral surface of the illuminating device or from 0.5 mm to 1 mm from the surface.

When the coating composition is applied in this manner, capillary forces will promote coating of the lateral edges of the illuminating device more rapidly.

A dispenser can be used to add the specified amount of coating composition required to specify the location. This dispenser can be a syringe or a needle or nozzle system. The easiest way to deposit a coating is to apply a drop of coating composition by using a syringe, needle or nozzle with a controller to dispense the desired droplet volume, usually by adjusting the dispensing time and pressure.

However, this addition can also be achieved by printing or spraying the coating composition, such as by using screen printing or ink jet nozzles or spray nozzles.

Coating can be facilitated by coating the lateral surface with capillary force. The coating typically occurs by self-wetting in about 1 or 2 seconds.

Coating can also be achieved by applying a liquid coating composition to the sub-substrate around the illuminating device to force the fluid to contact the fill region. In this case, the nozzle or needle translates in a controlled and programmable manner while controlling the dispensing during this movement. This is an advantage if the coating fluid has poor wetting on the material of the device to be coated and it provides a means of coating only certain sides. Poor wetting prevents self-wetting, but dispensing fill forces the fluid to spread. The disadvantages are the more critical placement accuracy and additional processing time required.

Combinations of filling and self-wetting can also be achieved, for example, by moving the nozzles in a line that is close to a plurality of LED devices that are spaced apart by a short distance and placed in a straight line, and that dispenses while moving the nozzles in a straight line. The applied fluid interacts with the edges of the LED device and self-wetting at its circumference.

The coating composition is a liquid composition which may contain a sol-gel monomer such as an alkyl alkoxysilane such as methyltrimethoxydecane or a polyoxyxylene resin. The sol-gel monomer can be (partially) hydrolyzed and polymerized in a liquid which can contain water and/or alcohol. This type of fluid is therefore generally hydrophilic (polar). It can contain one or more solvents in various amounts to tune the viscosity of the fluid. The polyoxyxene resin is typically a fluid in a non-cure form and can be used similarly or, as the case may be, to adjust the viscosity of the fluid. Polyoxyxylene resins are found in many chemical compositions and materials properties from a variety of suppliers. Viscosity and material properties can vary after curing (from the change of the elastomeric gel to the hard polyoxyxide coating). Depending on the type of polyoxyxene resin, an example of such a solvent may be xylene. The polyoxygenated fluids are typically (but not necessarily) non-polar.

The extent to which the fluid is polar or non-polar can be affected by the exact fluid composition, such as the type and amount of solvent used.

The coating composition used in the present invention is a coating composition which forms a scattering, absorbing, luminescent, diffusing or reflecting coating layer (i.e., a photoactive coating layer) upon solidification. There are many examples of compositions that can be used for this purpose.

In the present invention, it is also understood by "solid" that the coating layer can be amorphous.

Typically, the scattering, absorbing, luminescent, diffusing or reflecting particles are dispersed in a composition which preferably has a low viscosity.

For example, scattering particles such as metal oxides, reflective, diffusing or luminescent metal flakes and/or absorbing dyes or pigments may be dispersed in the coating composition.

For example, TiO ₂ particles having, for example, a submicron diameter can be used as the inorganic scattering particles. By using a suitable loading, such as 5v% to 60v% of the particles, a low loss scattering reflective coating can be achieved at a thickness exceeding, for example, 5 microns.

The coating composition is solidified to obtain a solid coating layer on the lateral surface. Coagulation can occur by any coagulation action (eg, by air drying the coating to remove the solvent, and/or typically curing the coating at elevated temperatures). As an example, for solidification of a sol-gel monomer, the coating can be dried for about 10 minutes to evaporate most of the solvent (such as water and methanol) from the coating. Next, the coating was further dried at 90 ° C for 20 min, and thereafter, the sol gel was cured by curing at 200 ° C for 1 hr to form a brittle methyl silicate network.

The coating layer typically has a thickness of from 10 μm to 500 μm.

Thus, the coating composition is selected such that upon solidification, the solid composition obtained has the following optical functionality or a combination of such functions: typically by using scattering pigments (such as, for example, TiO ₂ , ZrO ₂ and Al) ₂ O ₃ metal oxide particles) reflective functionality. A less preferred alternative is by using metal flakes or granules or holes. By coating the lateral edges with a coating composition having this functionality, the light transmission through the side coating will be small and will reflect most of the light (eg, 95%).

This choice of functionality solves the problems 1 to 4 described in the background section. The drawback is that a small amount of reflected side light may be reabsorbed and lost by the LED. Again, the brightness of the top surface is increased, for example, by coating a 1 x 1 mm LED die on the side of a 120 micron thick phosphor to achieve a typical brightness gain of 10% to 15% in the normal direction.

By using scattering pigments (such as _{TiO 2, ZrO 2, Al 2} O 3 and the metal oxide particles of SiO ₂₎ of the diffusion functionality. This allows for (partial) light transmission through the side coating, wherein the amount of forward and backscattering can be controlled by the volume concentration and particle size of the pigment as well as the thickness of the coating.

This functional part addresses the problems 1 and 2 described above, but does not solve problems 3 and 4. The benefit is that less light is directed back to (generally) lossy LEDs than reflective functionality.

Use of colored or color pigment spectral filter functionality. Typically, the colored layer will absorb blue LED light and transmit the converted light from the phosphor. This solution is especially for problem 1 of fully converting Lumiramic, but does not solve problems 2, 3 and 4.

For partial conversion, the blue light absorbs the risk of color shift across the angle by absorbing too much blue light. Fine adjustment of the absorption characteristics is required so that partial absorption of blue light leakage overcomes this problem.

The benefit is an increased total luminous flux compared to the reflective functionality.

By using the absorption functionality of the pigment that absorbs the incident light flux spectrum. This solves most of the problems, but will result in severe loss of luminous flux and will not increase the brightness of the top surface and is therefore less preferred. The absorbance can be complete or only partial depending on the nature, concentration and layer thickness of the absorbing pigment or dye.

The luminescent functionality of luminescent pigments/particles that provide the same or different luminescence spectrum as the phosphor is used. Blue light leakage through the sides will be absorbed and converted to higher wavelengths. This will solve the problem 1 especially for fully converting phosphors, but does not solve problems 2, 3 and 4. It also slightly increases the area of the light source. The benefit is the desired increased total luminous flux compared to the reflective functionality.

Thus, for embodiments of the present invention, combinations of different coating layers having different functionalities may be considered depending on the desired functionality, or different functionalities may be combined in the same coating, such as diffuse functionality and illuminating function. Sexual combination.

The submount and the lateral surface may be pretreated in a manner that becomes polar (or hydrophilic) and the coating composition may be polar (or hydrophilic). The hydrophilic (polar) coating composition will then be promoted by capillary forces to cover the treated sub-substrate and the lateral surface. By treating only a portion of the submount and the lateral surface to become hydrophilic, it is possible to coat only portions of the lateral surface, as shown in FIG. Similarly, by using a non-polar (or hydrophobic) coating composition (such as most polyoxo) on a polar (or hydrophilic) surface, limited fluid dispersion can be achieved, or non-polarity can be achieved ( Or hydrophobic) good dispersion on the surface. Therefore, it is also possible to process portions of the sub-substrate and the lateral surface to become non-polar (or hydrophobic), and therefore, by using a polar (or hydrophilic) coating composition, portions of the lateral surface will be uncoated. Floor. Obviously, the surface wetting conditions of the sub-substrate and the lateral side surfaces of the device may not be identical, and a better dispersion on the sub-substrate or lateral side may be achieved. Also, the lateral side surfaces are typically comprised of multiple components such as LED materials, bonding materials, LED substrates, or phosphors. Priority wetting of these various materials can occur. For example, if the phosphor has poor wetting conditions for the coating fluid, side coverage of the phosphor may not be achieved or only limited side coverage of the phosphor may be achieved, and for example, the binder and the LED die may be covered.

By tuning the humidification conditions on the surface of the LED (eg, by tuning the oxygen plasma or UV ozone treatment of the LED device), the amount deposited, and/or by increasing or tuning the viscosity of the coating composition, or Another way to coat only portions of the lateral surface is achieved by adding a solvent having a faster evaporation effect.

In principle, the coating composition can be deposited using techniques that also cover the top of Lumiramic, such as knife coating, spin coating, spray coating, dip coating or curtain coating. Especially in the case of a reflective coating, a moisture resistant layer should be placed on top of the Lumiramic surface. If sufficient moisture resistance is present, in the case of a hydrophobic coating composition, since the coating is not energetically resistant to covering the wet top surface, the coating will tend to flow to the side so that no thin layer remains on the top Or just keep a thin layer. A sufficiently thin layer of the reflective coating at the top will still be partially transmissive and may be allowed. The moisture resistant layer may be comprised of a hydrophobic coating layer (e.g., a hydrophobic decane monolayer treated with a fluorodecane top surface of the phosphor). For diffuse, luminescent, colored coating compositions, the top surface coverage is allowed. Diffusing the top coating can help redistribute the light distribution to achieve a more uniform color-over-angle. A luminescent or colored top coat can help reduce the blue light leakage from the top surface of the fully converted phosphor application.

This is especially important in the case where a large amount of coating composition is added. The moisture resistant layer can be a solid, a liquid or a gel. It may be a volume layer, but may also be a single layer deposited on the top surface of Lumiramic (for example, a hydrocarbon decane or a fluorodecane that has reacted with the surface of the phosphor from the gas phase).

However, methods to avoid spillage of the top surface are preferred, especially for reflective coating formulations.

The viscosity of the composition can be chosen such that the composition is low enough to be easily spread by capillary forces around the illumination device. Therefore, the viscosity can be between 1 mPa and 100 mPa.

Also, the viscosity of the fluid can be reduced by heating the fluid and/or device.

It is also possible to control the area coated by the coating composition by controlling the viscosity. For example, if a lower viscosity is used, the coating composition will spread more easily and the coating will appear more quickly. On the other hand, if a higher viscosity is used, the coating composition will tend to spread less easily and it will become possible to coat only a portion of the lateral surface.

When good wetting is achieved on the lateral surface, the contact angle of the solid coating layer can be between 0 and 45 degrees. When a low contact angle is achieved by the present coating method, only a small amount of material is required to coat the lateral surface, which may be preferred.

In addition, this has the benefit that the light source will not be significantly magnified, the side coating thickness (and therefore the optical properties) can still be reasonably controlled, and the less stress is due to the shrinkage stress that would normally occur in the curing of the side coating. To the side coating and LED device. The sharp contour that can be achieved has a minimal risk of guiding the light entering the side coating.

Thus, a less preferred embodiment of a side coating using a coating composition is disclosed that exhibits undesirable wetting on a lateral surface or a particular lateral surface. As a result, the contact angle at the lateral surface will be large (eg, between 45 and 90 degrees, or even more than 90 degrees). The surface coverage of the lateral surface may be incomplete depending on the amount of application. The coated regions or layers can be controlled by tuning the amount deposited. For example, it is possible to cover only the LED and the bonding layer without covering a substantial portion of the Lumiramic phosphor. Thus, the light leakage paths 1 and 2 can be suppressed, and the path 3 is still leaked through. The advantage is that more light can be extracted from the LED, and the side light leakage is suppressed due to changes in the thickness of the adhesive. Cross-angle color performance is still sufficient for practical use. For adequate coverage, a large amount of material is required. Also, for colored, slightly diffused or luminescent layers, there is a high risk of guided waves in this side coating which will unfold light without substantial light extraction, which is extremely undesirable for us.

In another embodiment of the invention, the second liquid coating composition is applied to the submount such that it will cover at least a portion of the second lateral surface of the illumination device. The second coating composition is solidified to obtain a second solid coating layer on at least a portion of the second lateral surface. Similarly, a plurality of coating layers may be deposited on top of each other.

When the light-emitting device is coated by different coating compositions in the first coating layer and the second coating layer, it is possible to achieve different solid coatings with reflection, diffusion, spectral filtering, luminescence, and light blocking optical functionality. Floor. Thus, the same lateral surface can be coated by more than one coating layer having the same or different optical functionality.

Thus, different portions of the lateral surface can have different optical functionality.

The coating disposed on the lateral surface of the device is in close proximity to the lateral side and is in substantial contact. However, due to shrinkage stress, insufficient adhesion, thermal stress, physical contact of the side coating with the lateral sides (parts) and with the sub-substrate (part of) can be disrupted. As a result, a small gap can exist where the contact is broken. This does not necessarily impede the functionality of the side coating.

Even though the invention has been described with reference to the specific exemplary embodiments of the invention, many variations, modifications, and the like will become apparent to those skilled in the art. The described embodiments are therefore not intended to limit the scope of the invention as defined by the appended claims.

1. . . Illuminating device

2. . . Flip chip light emitting diode (LED)

3. . . Subsubstrate

4. . . Optical component

4a. . . Phosphor / Lumiramic Phosphor

4b. . . Substrate

4c. . . Reflector

5. . . Bonding layer

6. . . Transverse surface / lateral circumferential surface

7. . . Photoactive coating layer

7a. . . Second coating layer

7b. . . First coating layer

8. . . Top surface

I. . . Ray collection

II. . . Ray collection

III. . . Ray collection

IV. . . Ray collection

Figure 1 is a schematic cross-sectional view showing an embodiment of a top emission illuminating device having a Lumiramic phosphor of the present invention, wherein the lateral circumferential surface is coated by a reflective coating layer;

Figure 2 is a schematic cross-sectional view showing another embodiment of a top-emission illuminating device having an angular Lumiramic phosphor of the present invention, wherein the lateral circumferential surface is coated by a reflective coating layer;

Figure 3 is a schematic cross-sectional view showing another embodiment of a top emission light-emitting device having a Lumiramic phosphor of the present invention, wherein the lateral circumferential surface is coated by two coating layers;

Figure 4 is a schematic cross-sectional view showing another embodiment of a top-emission illuminating device having a substrate of the present invention, wherein the lateral circumferential surface is coated by a reflective coating layer;

Figure 5 is a schematic cross-sectional view showing an embodiment of a side-emitting light-emitting device of the present invention, wherein a portion of the lateral circumferential surface is coated by a reflective coating layer;

Figure 6 is a schematic cross-sectional view showing an embodiment of a side-emitting light-emitting device having a substrate and a phosphor of the present invention, wherein a portion of the lateral circumferential surface is coated by a reflective coating layer;

Figure 7 is a schematic cross-sectional view showing an embodiment of an array of light-emitting devices of the present invention, wherein a portion of the lateral circumferential surface is coated by a reflective coating layer;

8a to 8c schematically illustrate a perspective view of a method for coating a lateral circumferential surface of a light-emitting device; and

Figure 9 illustrates a perspective view of one embodiment of a light-emitting device of the present invention in which a portion of the lateral circumferential surface is coated by a reflective coating layer.

1. . . Illuminating device

2. . . Flip chip light emitting diode (LED)

3. . . Subsubstrate

4a. . . Phosphor / Lumiramic Phosphor

5. . . Bonding layer

6. . . Transverse surface / lateral circumferential surface

7. . . Photoactive coating layer

8. . . Top surface

I. . . Ray collection

II. . . Ray collection

III. . . Ray collection

IV. . . Ray collection

Claims (19)

A light-emitting device (1) comprising a light-emitting diode (2) disposed on a sub-substrate (3), the device having a lateral circumferential surface (6) and a top surface (8), and a photoactive (optically active) a coating layer (7) covering: at least a portion of the circumferential surface (6), extending from the sub-substrate (3) to the top surface (8), and substantially The top surface (8) is not covered, wherein the photoactive coating layer is selected from the group consisting of a diffuse coating layer, a spectral filter coating layer, a light-emitting coating layer, and a light-blocking coating layer, and combinations thereof. The illuminating device of claim 1, further comprising an optical component (4) disposed on the light emitting diode, the optical component (4) being selected from the group consisting of a phosphor, a light transmitting body, and a reflector, and The group of its combination. The illumination device of claim 2, wherein the reflector is configured such that light will escape through at least a portion of the lateral circumferential surface. The illuminating device of claim 1, further comprising an optical component disposed on the illuminating device. The illuminating device of claim 1, wherein the coating layer is a solid. The illuminating device of claim 1, wherein the at least a portion of the lateral circumferential surface is coated by more than one coating layer. An array of illumination devices comprising a plurality of illumination devices as claimed in any one of claims 1-6. The array of illumination devices of claim 7, wherein the illumination devices are configured to share the coating layer. A method for applying a coating layer on at least a portion of a lateral circumferential surface (6) of a light-emitting device (1) comprising a light-emitting diode, the method comprising: at least at the circumferential surface (6) a light-active coating layer (7) is disposed on a portion thereof, the coating layer (7) extending from the sub-substrate (3) to the top surface (8), and substantially not covering the top surface (8), wherein the light The active coating layer is selected from the group consisting of a diffuse coating layer, a spectral filter coating layer, a luminescent coating layer, and a light-blocking coating layer, and combinations thereof. The method of claim 9, further comprising the step of: coating a first liquid coating composition on the sub-substrate (3), allowing the first coating composition to cover one of the light-emitting devices (1) At least a portion of the transverse circumferential surface (6), and solidifying the first coating composition to obtain a first solid coating layer (7) on the at least a portion of the first lateral circumferential surface (6). The method of claim 10, wherein the coating composition permits at least a portion of a first lateral circumferential surface (6) to be covered by capillary force. The method of claim 10 or 11, wherein the coating composition is applied by a method selected from the group consisting of needle dispensing, nozzle dispensing, printing, and spraying. The method of claim 10 or 11, wherein the liquid coating composition, after solidification, forms a layer selected from the group consisting of a diffusion coating layer, a spectral filter coating layer, a light-emitting coating layer, and a light-blocking coating layer, and A combined solid coating layer of the group. The method of claim 10 or 11, wherein the coating composition comprises a sol-gel derived material or a polyoxynoxy resin. The method of any one of claims 9 to 11, further comprising pretreating the lateral circumferential surface to become polar and using a polar coating composition. The method of any one of claims 9 to 11, further comprising pretreating the lateral circumferential surface to become non-polar and using a non-polar or polar coating composition. The method of any one of claims 9 to 11, further comprising the step of coating at least one second liquid coating composition on the sub-substrate, allowing the second coating composition to cover one of the illuminating devices At least a portion of the lateral circumferential surface, and solidifying the second coating composition to obtain a second solid coating layer on the at least a portion of the second lateral circumferential surface. The method of claim 17, wherein the first coating composition is different from the second coating composition. The method of claim 17, wherein the first lateral circumferential surface is different from the second lateral circumferential surface.